(1) Field of the Invention
The invention is related to an apparatus for automatic, continuous production of preforms according to the preamble of claim 1 and to a process for automatic, continuous production of preforms with such an apparatus according to the preamble of claim 6.
(2) Description of Related Art
Definitions
Preforming routines can be divided into direct and sequential preforming routines.
Direct preforming routines like “Fiber Placement” or “Tailored Fiber Placement” allow a customized positioning of fiber bundles (rovings) but imply a low material deposition speed.
Sequential Preforming routines mostly use the stitching technology, the binder technology or a combination of both to process fabrics from rolls. The stitching routine is a highly automated, sequential process. In order to enable a compaction of the preform over the whole surface (“final-thickness-compaction”) by means of stitching, a high seam density has to be chosen, which results in a high degree of fiber distortion and a long process time. Within the Binder routine the preform needs to be compacted and heated up above the binder softening temperature at usually ˜100° C. The compaction is done with a mostly non-reusable vacuum bagging which is applied manually. The binder activation is a time and energy consuming step which is conducted in a convection oven or infrared field.
The document WO 2009156754 (A1) discloses a method of fabricating a fibre reinforced thermoplastic composite structure comprising: placing a first layer of fibre reinforced thermoplastic material on top of a second layer of fibre reinforced thermoplastic material; providing a local heating source and locally heating a portion of at least the upper layer of thermoplastic composite material; and providing an ultrasonic transducer and locally introducing ultrasonic energy waves to the heated portion of the thermoplastic material such that ultrasonic consolidation of the fibre reinforced thermoplastic occurs.
The document U.S. Pat. No. 4,404,052 (A) discloses a method and apparatus for bonding together a plurality of juxtaposed webs which are subject to being ultrasonically bonded together to form a laminate as the webs are being driven forward at a relatively high velocity. The regions of the webs to be bonded are subjected to progressively increasing compressive forces while simultaneously being subjected to ultrasonic energy as they traverse an elongate portion of a predetermined path at a predetermined velocity. After the regions are ultrasonically bonded they may be subjected to another compression prior to the bonds becoming fully set upon cooling. The method may be practiced in an apparatus which includes an ultrasonic horn and an anvil which are configured and disposed to define a bonding passageway having an elongate convergent portion; and the apparatus may include a pressure roll biased towards the anvil adjacent the downstream end of the passageway. A face of the ultrasonic horn is so curved in the machine direction that the passageway has a convergent-divergent arcuate shape; the entrance to the passageway is sufficiently high to obviate web-splice induced jams.
The document DE 4105013 A1 describes a process and apparatus to weld endless material quasi-continuously using ultrasonic technology with a rotating anvil. The material is transported intermittent; there is no relative movement between horn and material during welding.
The document U.S. Pat. No. 6,432,236 describes a method to fabricate a composite structure by using ultrasonic technology and fiber reinforced tapes with a thermosetting matrix. The material is laid up under pressure and under induction of ultrasound in order to suppress voids/air entrapment. The ultrasonic unit is moved along the composite structure for consolidation.
The document WO 2007/003626 A1 describes a method to assemble rigid fiber reinforced thermoplastic parts by means of ultrasonic welding. In order to ensure a softening of the material in the interface, energy directors are brought into the interface.
Neither of the cited methods and apparatuses is suitable to automatically and continuously produce preforms for components of fiber reinforced plastics.